1. Technical Field
The present invention relates to a fluid ejection device in which a drive signal is applied to an actuator to eject fluid, and is suitable for a fluid ejection printer adapted to, for example, eject small droplets from a nozzle of a fluid ejection head to form fine particles (dots) on a print medium, thereby printing a predetermined character, image, or the like.
2. Related Art
In the fluid ejection printer, there is provided an actuator such as a piezoelectric element in order for ejecting a droplet from the nozzle of the fluid ejection head, and it is required to apply a predetermined drive signal on the actuator. Since the drive signal has a relatively high voltage, it is required to power-amplify a drive waveform signal forming a basis of the drive signal with a power amplifier circuit. Therefore, in JP-A-2007-168172 (Document 1), there is used a digital power amplifier circuit, which has a smaller power loss compared to an analog power amplifier circuit and can be made smaller in size, a modulator executes pulse modulation on the drive waveform signal to obtain a modulated signal, the digital power amplifier circuit performs power amplification on the modulated signal to obtain a power-amplified modulated signal, and a low pass filter smoothes the power amplified modulated signal to obtain the drive signal.
In the fluid ejection printer described in the Document 1 mentioned above, the digital power amplifier circuit continues to operate even in the case in which the voltage of the drive signal does not change. Since the piezoelectric element used as the actuator of the fluid ejection printer is a capacitive load, even in the case in which the current supply to the actuator is stopped, the voltage of the actuator is kept at the voltage applied immediately before the stoppage. In other words, since the drive signal applied to the actuator or the drive waveform signal forming a basis thereof has a portion (period) with a voltage kept constant, it is not necessary to supply the actuator with a current when the voltage of the drive signal does not change. However, in the fluid ejection printer described in the Document 1 mentioned above, there arises a problem that the digital power amplifier circuit continues to operate, and therefore, the power is consumed in the digital amplifier circuit and the low pass filter even when the voltage of the drive signal does not change.